KVM: arm64: Just advertise SEIS as 0 when emulating ICC_CTLR_EL1

ICC_CTLR_EL1 accesses from a guest are trapped and emulated on systems
with broken SEIS support and without FEAT_GICv3_TDIR. On such systems,
we mask SEIS support in 'kvm_vgic_global_state.ich_vtr_el2' and so the
value of ICC_CTLR_EL1.SEIS visible to the guest is always zero.

Simplify the ICC_CTLR_EL1 read emulation to return 0 for the SEIS field,
rather than reading an always-zero value from the global state.

Cc: Marc Zyngier <maz@kernel.org>
Cc: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Will Deacon <will@kernel.org>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20241022144016.27350-2-will@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

Author: willdeacon

arch/arm64/kvm/hyp/vgic-v3-sr.c

@@ -1012,9 +1012,6 @@ static void __vgic_v3_read_ctlr(struct kvm_vcpu *vcpu, u32 vmcr, int rt)
 	val = ((vtr >> 29) & 7) << ICC_CTLR_EL1_PRI_BITS_SHIFT;
 	/* IDbits */
 	val |= ((vtr >> 23) & 7) << ICC_CTLR_EL1_ID_BITS_SHIFT;
-	/* SEIS */
-	if (kvm_vgic_global_state.ich_vtr_el2 & ICH_VTR_SEIS_MASK)
-		val |= BIT(ICC_CTLR_EL1_SEIS_SHIFT);
 	/* A3V */
 	val |= ((vtr >> 21) & 1) << ICC_CTLR_EL1_A3V_SHIFT;
 	/* EOImode */